Shock indicator

ABSTRACT

A shock indicator is described comprising (A) a base having a first side and a second side; (B) an indicator associated with the first side of the base, the indicator comprising a plurality of indicator subparts, the subparts comprising solid material arranged (i) in a first configuration when the shock indicator is in a first state prior to a shock event, and (ii) in a second configuration when the shock indicator is in a second state following a shock event; and (C) means associated with the second side of the base for attachment of the shock indicator to a surface. A method of manufacture is also provided.

This application claims the benefit of U.S. Provisional Application No.60/388,684, filed on Jun. 14, 2002.

FIELD OF THE INVENTION

The present invention relates to a shock indicator device, assembliesthat include the shock indicator device, and a method for themanufacture of the shock indicator device.

BACKGROUND OF THE INVENTION

Shock indicators are devices that may be applied to other devices withinany of a variety of different industries. Shock indicators are useful indetecting significant vibration or mechanical shock experienced by anassociated device such as an electronic device, including hand heldelectronic devices. Cellular phones, personal digital assistants, handheld computers, battery chargers, small electric appliances, digitalcameras (e.g., video and still cameras) are exemplary of devices thatmay be used in association with a shock indicator. Shock indicators maybe placed on the electronic device in a suitable manner, either on theouter surfaces of the device or on an internal surface such as adjacentelectronic components within the device, in the battery compartment orthe like. If the electronic device experiences a severe shock as mayoccur if the device is dropped onto a hard surface from a significantheight, the shock indicator should be activated to thereafter indicatethe occurrence of the shock. Such information could be useful to amanufacturer and/or a service organization charged with repair orreplacement of the device.

The vibration or shock history of an electronic device can be important.For example, recent developments in electronic equipment and componentshave provided a technological revolution in display technology. Previousmonochrome displays made of polymeric film and the like have beenrelatively forgiving when mistreated or otherwise subjected toconditions of extreme handling (e.g., dropping or other shock inducingevents). More recent developments in color displays have not yet evolvedto such a level of durability. Many color systems still require glasspanels which may be damaged when dropped or otherwise subjected to ashock force.

It would, therefore, be desirable to provide a shock indicator that canbe affixed to or otherwise associated with a device, such as anelectronic device including a cellular phone, a personal digitalassistant, a hand held computer and the like. It would be especiallydesirable to provide such a shock indicator device in a constructionthat allows for activation of the indicator when an associated apparatusor device experiences a significant shock event, regardless of thedirection of the force.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a shock indicator, comprising:

-   -   (A) A base having a first side and a second side;    -   (B) an indicator associated with the first side of the base, the        indicator comprising a plurality of indicator subparts, the        subparts comprising solid material arranged (i) in a first        configuration when the shock indicator is in a first state prior        to a shock event, and (ii) in a second configuration when the        shock indicator is in a second state following a shock event;        and    -   (C) Attachment means associated with second side of the base for        attachment of the shock indicator to a surface.

The subparts of the indicator may comprise material selected from thegroup consisting of toner powder particles, talc, flour, pigment, clay,ceramics, alumina, metals, and combinations of the foregoing, and thesubparts may be surface modified. In another aspect, the subparts of theindicator may comprise a first size and the indicator may furthercomprise another component comprising a second subpart having a secondsize larger than the first subpart such as glass beads, for example.Typically, the shock indicator will also comprise a containment memberdisposed on the first side of the base and enclosing the indicatortherein, the containment member being transparent, thereby facilitatingthe visual determination of the indicator in either its first or secondconfiguration. The indicator and the first side of the base may beprovided in different colors to provide a visual contrast therebetween.

In another aspect, the shock indicator may further comprise adifferentiating component associated with the first side of the base thedifferentiating component comprising a film material to enhance thevisual contrast between the differentiating component and the indicator.The differentiating component may comprise a first side and a secondside and an annulus extending through the differentiating component fromthe first side to the second side, the indicator positioned within theannulus, at least one of the first side or the second side of thedifferentiating component comprising a structured surface. Thestructured surface may be a microstructured surface which is associatedwith the first side of the base to define a plurality of channelsarranged in a predetermined pattern, the channels comprising an openingto permit the ingress of fluid when the indicator is in a second state.The microstructured surface typically comprises a regular array ofprecise structures having a shape selected from the group consisting ofsymmetrical shapes and asymmetrical shapes.

In still another aspect, the shock indicator may further comprise animpingement object within the containment member and positioned toimpact the indicator during a shock event to aid in transitioning theindicator from the first state to the second state, the impingementobject can be a material selected from the group consisting of glassbeads, glass bubbles, ceramic beads, plastic beads, ball bearings andcombination thereof.

In another aspect, the indicator comprises dry materials and the shockindicator further comprises means to indicate exposure to wetness.

In still another aspect, the indicator comprises an agglomerated powderin the first state prior to a shock event and a dispersed powder in thesecond state following a shock event, the indicator subparts comprisingparticles of the powder. Also, the indicator may comprise a solid (e.g.,powder) and a liquid wherein the solid may be selected from the groupconsisting of exfoliated organophilic clay fillers, silica particles,glass particles, inorganic pigments, and combinations of the foregoingand the liquid at 23° C. has a surface tension within the range fromabout 10×10⁻³ N/m to about 80×10⁻³ N/m, a density from about 0.5 toabout 2 grams/cm³, and a zero rate shear viscosity from about 1×10⁻³ toabout 1×10⁶ Pa-s. Some suitable fluids comprise liquids selected fromthe group consisting of silicone fluids and oils, saturatedhydrocarbon-based oils, silicone gums, mineral oil, glycerols, water andcombinations of the foregoing.

In still another aspect, the shock indicator further comprises atransmission layer positioned on the first side of the base between thebase and the indicator, the transmission layer comprising a material toreduce, maintain or increase shock force transmitted to the indicatorduring a shock event. In other aspects the transmission layer comprisesa viscoelastic material having a storage modulus of at least about 1.0psi (6.9×10³ Pascals) and a loss factor of at least about 0.01 at thetemperature and frequency at which the shock indicator is used.

In still another aspect the invention provides an assembly comprisingthe above mentioned shock indicator associated with an electronic deviceselected from the group consisting of cellular telephone, personaldigital assistant, and hand held computers.

In another aspect, the invention provides a method for the manufactureof a shock indicator, comprising:

-   -   (A) providing a base comprising a first surface and a second        surface, the second surface of the base associated with an        attachment means; and    -   (B) placing an indicator in association with the first surface        of the base, the indicator comprising a plurality of indicator        subparts, the subparts comprising solid material arranged (i) in        a first configuration when the shock indicator is in a first        state prior to a shock event, and (ii) in a second configuration        when the shock indicator is in a second state following a shock        event.

The step of placing an indicator in association with the first surfaceof the base may further comprise placing a plurality of indicators inassociation with the first side of the base, each indicator comprising aplurality of indicator subparts, the subparts comprising solid materialarranged (i) in a first configuration prior to a shock event, and (ii)in a second configuration following a shock event.

In another aspect, placing an indicator in association with the firstsurface of the base is accomplished by screen printing the indicatoronto the first surface.

In still another aspect, the invention provides the foregoing method andfurther comprises placing a containment member over the first side ofthe base and over the indicator, the containment member beingtransparent, thereby facilitating the visual determination of whetherthe indicator is in the first configuration or the second configuration.

In still another aspect, the invention provides the foregoing method andfurther comprises providing a differentiating component associated withthe first side of the base the differentiating component comprising afirst side and a second side and an annulus extending through thedifferentiating component from the first side to the second side, one ofthe first side or the second side comprising a structured surface; andplacing an indicator in association with the first surface of the basefurther comprises placing the indicator within the annulus. Thestructured surface can comprise a microstructured surface associatedwith the first side of the base, the microstructured surface comprisinga regular array of precise structures having a shape selected from thegroup consisting of symmetrical shapes and asymmetrical shapes, theprecise structures defining a plurality of channels arranged in apredetermined pattern, the channels comprising an opening to permit theingress of fluid within the channels when the indicator is in a secondstate.

In another aspect, the method will also comprise providing a means forattaching the indicator to another surface such as by an adhesive or amechanical fastener, for example, herein the means for attaching maycomprise a material to reduce, maintain or increase shock forcetransmitted to the indicator during a shock event.

In still another aspect, the invention provides the foregoing method andfurther comprises providing a transmission layer in association with thefirst side of the base between the base and the indicator, thetransmission layer comprising a material to reduce, maintain or increasethe shock force transmitted to the indicator during a shock event.

In still another aspect, the invention provides the foregoing method andfurther comprises associating an electronic device with the shockindicator, the device selected from the group consisting of cellulartelephone, personal digital assistant and hand held computer.

Additional details of the invention will be more fully appreciated bythose skilled in the art upon further consideration of the remainder ofthe disclosure, including the detailed description of the preferredembodiment in conjunction with the various figures herein and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In describing the preferred embodiment of the invention, reference ismade to the various figures in which the features of the preferredembodiment are generally designated by reference numerals and whereinlike reference numerals indicate like structure, wherein:

FIG. 1 is a perspective view of one embodiment of a shock indicatoraccording to the present invention;

FIG. 2 is a cross sectional side elevation view of the shock indicatorof FIG. 1;

FIG. 3 is a top plan view of the shock indicator of FIG. 1 in a firststate prior to a shock event;

FIG. 4 is a top plan view of the shock indicator of FIG. 1 in a secondstate following a shock event;

FIG. 5 is a side elevation view of a material useful as a base in theshock indicator of the present invention; and

FIG. 6 is a schematic illustrating a method for the manufacture of theshock indicator of the present invention;

FIG. 7 is an exploded view, in a side elevated cross section, of anotherembodiment of a shock indicator according to the present invention;

FIG. 8 is a cross sectional side elevation view of the shock indicatorof FIG. 7 in a first state prior to a shock event;

FIG. 9 is a cross sectional side elevation view of the shock indicatorof FIG. 7 in a second state following a shock event; and

FIG. 10 is a cross sectional side elevation view still anotherembodiment of a shock indicator according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a shock indicator suitable for use on anyof a variety of shock-sensitive machines, electronic components,electronic equipment or other devices that may be subjected to inertialand vibrational forces during use. The shock indicator device of thepresent invention provides a passive means to determine whether anassociated apparatus or the like has been subjected to a mechanicalshock event. The shock indicator device of the invention is initiallyprovided in a non-activated condition and is transitioned to anactivated condition upon the application of sufficient force or shockcaused by, for example, the deceleration of an associated device droppedonto a floor or other hard surface from a significant distance.

Various features and embodiments are contemplated within the scope ofthe invention and are generally described below.

Referring now to the drawings, FIGS. 1 and 2 show a shock indicator 10according to the present invention. The shock indicator 10 may beaffixed to a surface 30 (see FIG. 1) of another device, as mentionedherein. The shock indicator 10 includes a base member 12 having a firstside 22 and a second side 24. The first and second sides 22 and 24 ofthe base member 12 comprise, respectively, the first and second majorsurfaces of the base member 12. An indicator 14 is associated with thefirst side 22 of the base 12. As shown, the indicator 14 can comprise aspherically configured agglomerated powdered material. The indicatormember 14 may comprise a colored powder and/or one or more coloringagents to provide the indicator 14 with a visually discernableappearance. If desired, portions of the indicator 14 may be provided inone or more colors while other portions of the indicator 14 may beprovided in another color or colors.

The indicator 14 is an agglomerated powder which, when so agglomerated,indicates a first or non-activated configuration prior to the occurrenceof a shock event. In the depicted embodiment, a domed containment member18 is provided over the first side 22 of the base member 12 andenclosing the indicator 14. As is described below, at least a portion ofthe domed containment member 18 is typically transparent in order tofacilitate the visual observation of the indicator 14. The containmentmember 18 functions to protect the agglomerated powder material of theindicator 14 from prematurely dispersing or smearing due to handling,incidental bumping, and the like. It will be appreciated that, in someembodiments, the containment member 18 may be considered an optionalcomponent such as when the shock indicator 10 is incorporated within adevice that includes a structure or structures equivalent to containmentmember 18, or where the indicator 14 is bound together in sufficientstrength to withstand smearing or activation during the normal andexpected use of the associated device. Additionally, the containmentmember may be provided in any of a variety of shapes and sizes as may berequired due to spatial constraints in a particular application or asmay be desired for any other reason. An attachment means 16 is alsoprovided and is associated with the second side 24 of the base member12. In the depicted embodiment of the shock indicator 10, the attachmentmeans 16 is a pressure sensitive adhesive. Other means for theattachment of the devices of the invention to a surface are alsocontemplated as within the scope of the invention.

It should be appreciated that the design and material selection for theattachment means 16 may affect the level of force that actually actsupon the indicator 14 and the associated parts of the shock indicatordevice 10. The indicator 14 will respond to a level of force that causesthe subparts of the indicator 14 to disperse. The shock event can leadto shear, compression, tensile, peel or cleavage stress forces acting onthe indicator and on the attachment means. The shock stresses impartedthrough, into or onto the indicator 14 will exceed the structuralstrength of the indicator 14 and/or the attachment means, causing thestructure of the agglomerated indicator 14 to collapse, fail,break-apart, disintegrate, implode, explode, disperse or change to thusindicate that a significant shock event has occurred. In the embodimentof FIG. 2, a release liner or liner material 26 may be provided toprotect the adhesive surface of the attachments means 16 prior to theshock indicator 10 being applied to a surface.

In the embodiment of FIG. 2, a release liner or liner material 26 may beprovided to protect the adhesive surface of the attachments means 16prior to the shock indicator 10 being applied to a surface.

An additional differentiating component 20 is may be provided over atleast a portion of the first surface 22 of the base member 12. Thedifferentiating component 20 may comprise a film material overlying thefirst side 22 of the base member 12. Most typically, the differentiatingcomponent 20, when present, is provided with a suitable surface color toenhance the visual contrast between the differentiating component 20 andthe indicator 14. In this manner, the activation of the indicator 14 ismore readily observable where the contrast between the indicator 14 andthe differentiating component 20 have been selected to facilitate thevisual determination of the activation state of the indicator 14.Alternatively, the base 12 can be provided as a colored film to providethe same color contrast effect in conjunction with the color selectedfor the indicator 14.

Referring to FIGS. 3 and 4, the shock indicator 10 may comprise anadditional component in the form of a conductive layer 122 configured toact as a circuit upon the application of charge thereto. The conductivelayer 122 is constructed of a conductive metal or other material capableof providing an electrostatic charge to powder particles positionedwithin the innermost portion of the differentiating component 20. Thepresence of a conductive layer 122 provides a means by which thepowdered indicator 14 may be agglomerated during the manufacture of theshock indicator 10 by providing sufficient electrostatic charge tocoalesce individual powder particles into a cohesive mass to therebyform the spherically agglomerated indicator 14 in a first configurationor first state prior to the occurrence of a shock event.

Referring to FIG. 4, the shock indicator 10 is depicted followingactivation due to a shock event. Accordingly, the subparts (e.g., powderparticles) of the indicator 14 are in a second configuration dispersedacross differentiating component 120 on the first side of the basemember 12, thereby visually exposing more of the conductive layer 122.The conductive layer 122 of the shock indicator 10 provides one mannerby which the powdered indicator 14 may be agglomerated in an appropriateposition to indicate a first state for the shock indicator prior to ashock event. It will be appreciated by those skilled in the art thatother means are available to provide an agglomerated powder indicator,some of which are described herein. The present invention is not to belimited in any way by the use of a conductive layer 122. For example, abinder composition and/or a diluent liquid may be mixed with anappropriate powder suitable for use as an indicator. The diluent liquidmay be any of a variety of suitable organic liquids, especially thosecapable of wetting the powder and thereby displacing entrapped air. Mosttypically, such a diluent liquid or binder will be selected so as tohold the powder in an agglomerated state for a period long enough toposition the indicator in a first configuration within the shockindicator. Thereafter, the diluent liquid may be evaporated and thebinder used, if any, will not be of sufficient strength to prevent thepowdered indicator from dispersing to a second configuration following ashock event.

A principal starting material for the manufacture of the shock indicatorcomprises a web 210, depicted in FIG. 5. The web 210 may compromise amultilayered film or a number of different film and adhesive layersassociated with one another. A number of film layers may be desired orneeded to support the indicator and the containment member, if present.Additionally, one or more adhesives or other attachment means may beutilized to adhere the layers of the web 210 to one another as well asproviding an attachment means for affixing the shock indicator toanother device. In the depicted embodiment of the web 210,differentiating component layer 220 overlies silicone release coating222. The differentiating layer 220, when present, may be colored whereit is desirable to provide a visual contrast with the indicator in thefinished shock indicator. Release coating 222 is provided as aconvenience during the manufacture of the shock indicator to facilitatethe removal of excess background film 220 when the web 210 is used tomake a plurality of shock indicators. In this manner, the excessbackground film 220 may be removed as “weed” in the manner describedbelow.

A polymeric backing 224 is provided as a film associated with thesilicone release coating 222 by an adhesive layer 226 disposed along amajor surface of the polymer film backing 224. Along the opposite sideof the polymer film backing 224, another layer of adhesive 228 providesan attachment means for affixing the finished shock indicator to thesurface of another device or the like. Release liner 230 may overlay thesurface of the adhesive 228 to at least temporarily protect the surfaceof the adhesive layer 228.

Referring now to FIG. 6, a process for the manufacture of the shockindicator of the present invention will be described. The aforementionedweb 210 is conveyed along a converting line 300. A first rotary die 302is positioned along the converting line 300. The die 302 is configuredto cut a plurality of circular base members in the web 210. It will beappreciated that the configuration of the shock indicator, althoughdepicted herein as circular, may comprise any of a variety of shapes andsizes including circular, square, rectangular, oval, polygonal, and thelike. Following die cutting by rotary die 302, the web 210 advancesalong the converting line to roller 304 where the unneeded portions ofthe layer 220 (see FIG. 5) are removed as “weed” 306 which is directedto take up roll 308, leaving the web 210 to comprise a top layer ofcircular background film 220 that will serve as a differentiatingcomponent in an article of the invention.

In this embodiment, a rotary screen printing roll 310 is positionedalong the web converting line 300 to screen print the powdered indicatoronto the die cut circular portions on the web 210. The use of a rotaryscreen printing process for the deposition of indicator materials istypically accomplished using a suitable indicator material mixed with anappropriate amount of a binder material and/or diluent liquid. Suchmaterials may comprise materials that are not normally considered asbinders in many applications. For purposes of the present invention,suitable binders include mineral oil, for example, as well as othersolvents or materials that will aid in the agglomeration of theindicator material without evaporating. Additionally, organic (e.g.,hydrocarbon) liquids may be added to the binder to facilitate theformation of a slurry that can then be deposited, printed or otherwiseplaced on the base member. A diluent liquid may also be an activesolvent for a binder without being a solvent for the indicator material.In this manner, a diluent liquid can assist in initially holding theindicator powder materials to each other. Following the deposition of aslurry onto the base member or web 210, the liquid is allowed toevaporate while the binder remains associated with the powder andcontinues to hold the agglomerated powder in a cohesive mass until it isdisturbed by a shock event. Additionally, the foregoing diluent liquidsmay be used without binder so that, following the evaporation of theliquid, the powdered agglomerate is maintained in a cohesive mass byelectrostatic attraction or van der Waals forces. Other embodiments ofthe indicator as well as the other features of the shock indicator ofthe invention are also contemplated, and at least some of those aredescribed herein including indicators that incorporate liquids withpowder particles and those that incorporate solid materials other thanpowder particles or solid materials (other than powder particles) thatare used with powder particles, for example. The present invention isnot to be construed as limited to any particular indicator compositionor construction other than those constructions that are capable oftransitioning from a first configuration to a second configuration inresponse to a shock event. Moreover, the construction of the shockindicator device of the invention can be customized in order to providethe device with a sensitivity to shock events of a certain thresholdvalue or minimum magnitude.

In various embodiments, a containment member will be placed over theaforementioned backing pieces and indicator materials. The containmentmaterial 312 is typically a polymeric material. Suitable materials forthe containment material include materials capable of being vacuumedformed such as polycarbonate, polystyrene, polyolefin, acrylic polymersand also polyester polymers and copolymers. The containment material 312is supplied from feed roll 314 to the vacuum forming roll 316. Asmentioned, the containment member may be supplied as a dome or in someother configuration. In the depicted process, the configuration of thecontainment structure is formed on a forming roll 316 and thereafterapplied over the above-described based members and the rotary screenprinted indicator materials. The containment material 312 is appliedover the backing material and is affixed thereto by adhesive layer 226(FIG. 5) provided as a layer of the web material 210. A second rotarydie 318 is provided to die cut through the containment material 312 andthe remaining layers of the web 210 so that individual shock indicatorsare thereby formed and are carried on a common backing. The backing maycomprise a liner 230 to hold all of the shock indicators on a sheetuntil further cutting or slitting of the web 210 occurs. The “weed” fromthe containment material 312 is then taken up on take up roll 328. Inthe depicted embodiments, the take up roll 328 picks up the weed fromthe conveyor line with guide rolls 322 and 324 to guide the weed to thetake up roll. A slitter 326 is then provided to slit the web 210 intoelongate strips having a plurality of shock indicator buttons alignedthereon in a longitudinal manner. These longitudinal strips may then befurther cut or packaged, as desired for convenient dispensing or forautomated dispensing such as from a dispenser fitted with a magazinecartridge.

Regarding materials, the base 12 (FIGS. 1 and 2) may comprise any ofvariety of suitable materials such as polymeric film materials, wovenand nonwoven materials, paper, spun bonded materials and the like. Theindicator material is typically comprised of a solid material thatfurther comprises a number of solid indicator sub-parts. Most typically,the indicator material is a powder material capable of forming anagglomerated mass. Suitable materials for the indicator includeconventional toner powders, talc, flour, pigments, clays, ceramicpowders (boron nitride, silicon carbide, alumina, etc), sphericalalumina, powered metals, other finely ground materials and the like. Thepowders particles can be surface modified with various chemicaltreatments or coatings to modify their agglomerating ability and/or toimprove mixing, compounding and/or delivery to a location. The powdersor particulates can be provided in any of a variety of shapes, such asplatelets, spherical, pole like all with various feature aspect ratios.The powder or particulate component can be hollow, porous, solid or amixture of these. Combination of these features permits unique blendingof particles and powders with optional larger particles and polymer orresin matrixes. The agglomerates can also be made using larger “seed”bodies or a resin starved matrix design comprising particles or beadssuch as glass bubbles or microbubbles and the like. When seed bodies areused, the smaller powder particles will be attached to or associatedwith the larger seed particle to form an agglomeration of the smallerparticles around the larger seed bodies.

Other materials are also mentioned herein in the discussion ofindividual embodiments, and it is not intended that the invention belimited to any particular selection of materials for the indicator.

Regarding the attachment means, any of a variety of materials may beused to affix the shock indicators of the present invention to thesurface of another device or apparatus. Adhesives as well as reclosablefasteners such as hook and loop components, and mechanical fastenerssuch as snaps, hooks, clips, clamps, and rivets may be used in affixingthe shock indicator of the invention to a device such as, for example, acellular telephone, a hand held computer, or the like. Adhesivessuitable for use as the attachment means may be selected from any of avariety of adhesive materials such as pressure sensitive adhesives,thermally bonded adhesives (e.g., hot melts), ultra-violet activatedadhesives, room temperature curable adhesives, cold seal adhesives, selffusing adhesives, epoxies, thermoplastics, thermosets and the like.Typically, pressure sensitive adhesives are used to adhesively bond theshock indicator to a device.

It will be appreciated that the selection of the specific attachmentmeans may take into account how the attachment means will affect theshock indicator's response to a shock event. Different attachment meanscan effect how the indicator will respond to a shock event. For example,the attachment means can provide damping and/or isolation to the shockindicator. The geometry of the attachment means (e.g., whether it is asolid material, has holes or other cut-outs, and its thickness, width,and/or length), its configuration, materials used, modulus, and the likecan effect the properties of the attachment means such as the stiffness,softness or spring constant and the resultant damping can change how theshock indicator responds to a shock event. A soft and low modulusattachment means (such as a double coated foam) win change how a shockindicator responds to a same shock event as compared with a stiff, highmodulus attachment means (such as an epoxy adhesive with a high modulusor high glass transition temperature, Tg). A pressure sensitive adhesive(PSA) can have a degree of damping and isolation performance dependingon the polymer's Tg and the application geometry used. Moreover,different pressure sensitive adhesives (or other attachment means) canchange the transmissibility of the same shock force.

Pressure sensitive adhesives generally possess (1) aggressive andpermanent tack, (2) adherence to a substrate upon the application offinger pressure, (3) the ability to hold onto a substrate or adherendand (4) sufficient cohesive strength to be substantially cleanly removedfrom the adherend for ease of rework. Additives may be added to thepressure sensitive adhesive to impart and/or improve these properties.Suitable pressure sensitive adhesives will typically include theforegoing properties and the actual attachment means used in the shockindicator of the invention may comprise a single pressure sensitiveadhesive or a combination of adhesives. Suitable pressure sensitiveadhesives include those based on natural rubbers, synthetic rubbers,styrene block copolymers, polyvinyl ethers, poly(meth)acrylates,polyolefins and silicones, for example. Tackifiers may be added to theadhesive for improved tack. Suitable tackifiers may comprise rosin esterresins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins andterpene resins. Oils, plasticizers, antioxidants, UV stabilizers,hydrogenated butyl rubber, pigments, curing agents and combinationsthereof may also be found in the pressure sensitive adhesive usefulherein.

A useful pressure sensitive adhesive may be based on at least onepoly(meth)acrylate derived from, for example, at least onealkyl(meth)acrylate ester monomer such as isooctyl acrylate, isononylacrylate, 2-methyl-butyl acrylate, 2-ethyl-hexyl acrylate and n-butylacrylate; and at least one co-monomer component such as (meth)acrylicacid, vinyl acetate, N-vinyl pyrrolidone, (meth)acrylamide, vinyl ester,fumarate, styrene macromer, or combinations of the foregoing. A suitablepoly(meth)acrylate for use in the invention may be derived from about 0to about 30 wt. % acrylic acid and about 100 to about 70 wt. % of atleast one of isooctyl acrylate, 2-ethyl-hexyl acrylate or n-butylacrylate. More typically, the suitable poly(meth)acrylate is derivedfrom about 2 to about 10 wt. % acrylic acid and between about 90 andabout 98 wt. % of at least one of isooctyl acrylate, 2-ethyl-hexylacrylate or n-butyl acrylate.

Referring generally to FIGS. 7, 8 and 9, a shock indicator 410 accordingto another embodiment of the invention is shown and will now bedescribed. The shock indicator 410 comprises a base member 412 having afirst side 422 and a second side 424. The first and second sides 422 and424 of the base member 412 comprise, respectively, the first and secondmajor surfaces of the base member 412. An indicator 414 is associatedwith the first side 422 of the base 412. In the embodiment of theinvention illustrated in FIGS. 7 and 8, the indicator 414 comprises aliquid in addition to the solid materials previously described herein.It is contemplated that the indicator 414 may comprise, for example, asuspension of exfoliated organophilic clay fillers or the like dispersedin a liquid phase material such as, for example, mineral oil. Onesuitable combination of materials for the indicator 414 is exfoliatedorganophilic clay dispersed in mineral oil at about 16% by weight. Othermaterials are described below.

The indicator 414 depicted in FIGS. 7 and 8 is in a first configurationprior to the occurrence of a shock event. Domed containment member 418covers the first side 422 of the base member 412 and the indicator 414.Differentiating component 420 is provided over at least a portion of thefirst surface 422 of the base member 412. In this embodiment, thedifferentiating component 420 comprises sheeting or material havingoptical properties that enable a viewer of the material to readilywitness changes in color caused by liquid released from the indicator414 as it travels along surface 422. Suitable materials for thisapplication are discussed herein.

In this embodiment, the differentiating component 420 is typically cut(e.g., die cut) in an annular shape to surround the indicator 414 withinannulus 430 in which the indicator 414 nests when the indicator is inits first configuration prior to a shock event. The differentiatingcomponent 420 is provided with both a structured surface 420 a and anon-structured surface 420 b. The non-structured surface 420 b may belaminated to, adhesively affixed to, or otherwise associated with thedomed containment member 418. The structured surface 420 a of thecomponent 420 is textured, and typically comprises a microstructuredsurface, wherein the microstructured surface defines a plurality ofchannels 421 with a predetermined channel pattern when the surface 420 ais laminated to the base member 412. The maximum depth and width of thechannels is typically less than about 1,000 microns. The channels may ormay not be interconnected. The channels may, optionally, be formed froma series of projections on the surface 420 a. The description of thesurface 420 a is not meant to exclude webs, fabrics, porous materials,porous papers, porous membranes, etc., which may have channels, butwhich may be considered as not being of a predetermined pattern.Typically, the channel portion of the substrates of the invention isregular, orderly, and non-random, and the channels are in an array. Insome embodiments, each channel would be substantially identical oridentical to an adjacent channel. In some embodiments, one may wish tohave differing channel geometries and/or sizes, either widthwise acrossthe channel surface or lengthwise down the channeled surface.

The substrates comprising the optical differentiating component 420 maybe flexible, and therefore easier to attach to an intended surface.However, semi rigid and rigid substrates also may be useful according tothe invention. The differentiating component 420 may or may not beretroreflective depending on the particular embodiment. Examples ofuseful non-retroreflective substrates include, but are not limited to,microstructured substrates. The use of a retroreflective microstructuredsubstrate may provide a number of advantages to the articles of theinvention such as providing a highly visible fluid flow front in whichthe fluid frustrates total internal reflection in the retroreflectivesubstrate. It will also be appreciated that the differentiatingcomponent may be provided with dual textured surfaces or dual smoothsurfaces (e.g., differentiating component 20, FIGS. 1 and 2) as may bedesired for a particular application of the shock indicator of theinvention.

The flow of the fluid through the microchannels is generally passive inthat it is typically accomplished via capillary action. Gravitationaleffects may also influence the flow of fluid to at least a minor extent.The microstructured surface of the differentiating component cancomprise different shapes including symmetrical or asymmetrical shapessuch as, for example, rectangular, square, trapezoidal, ring,triangular, etc. Optionally, markings (not shown) may be placed on theshock indicator 410 to indicate the magnitude of a shock event. Themarkings may, for example, be placed along the surface 419 of thecontainment member 418 at calibrated intervals. Such markings may or maynot be evenly spaced depending on the construction of themicrostructured surface 420 a and the channels created thereby.Typically, the channel openings are located on at least one edge or sideof a substrate and the channels extend through the entire substratesurface to another end or edge of the substrate (typically an oppositeend or edge). The channels 421 may be interconnected to promote a moreeven fluid flow front.

Although the channels 421 may be provided using a textured surface 420 alaminated to a relatively flat surface of the base member 412, it isalso possible to provide channels that are internal to the substrate byjoining together two microstructured surfaces to provide channels thatwill accommodate a desired fluid flow. The resulting substrate may ormay not be retroreflective depending on the patterns joined together.These sheets can be held together by a variety of means includingadhesives, hot-melt bonding, and the like. Depending on the substrateshape and channel design, it may be desirable to seal the edges or sidesof the substrate to prevent leakage of fluid therefrom. The channels ofthe microstructured substrate can have a variety of shapes. Typicallythe channels within the substrate are similarly shaped. Examples ofuseful channel cross-sectional shapes include, but are not limited to,the following: v-shaped channels, u-shaped channels, semi-circle-shapedchannels, and square u-shaped channels. The channels when viewed fromabove, can be linear or non-linear. For example, they may be straight,curved, twisted, crooked, tortuous, etc. The channels may optionally beformed by a series of geometric projections, wherein the paths betweenthe projections become the channels. This would be the case forretroreflective cube-corner sheeting discussed later herein. Preferablythe channels of the substrate are planar.

The depth of the channels normally will range from about 5 to less thanabout 1,000 microns, typically from about 10 to about 500 microns, moretypically from about 25 to about 200 microns, and often from about 25 toabout 100 microns. The width of the channels normally range from about 5to about less than about 1,000 microns, typically from about 10 to about500 microns, more typically from about 25 to about 250 microns. Thespacing of the channels is such that a channel is generally within about5 to less than about 1,000 microns of another channel, typically fromabout 10 to about 500 microns, and often from about 10 to about 250microns. The shape, length, and number of channels on the substrate canvary depending on a number of factors such as the length of time desiredfor the fluid to run through the substrate, the particular fluid to beused with the substrate. A microstructured substrate tends to retain itsgeometry and surface characteristics upon exposure to the fluids used inthe articles of the invention. One suitable material is aretroreflective diamond grade sheeting available from 3M Company underthe designation “DG307.”

Examples of useful non-retroreflective substrates include, but are notlimited to, those disclosed in U.S. Pat. No. 5,728,446 (Johnston) andU.S. Pat. No. 5,514,120 (Johnston). These substrates provide for liquidmanagement films that facilitate desired rapid and uniform anisotropy ordirectionally dependent distribution of liquids and absorbent articlesusing these films. These liquid management film have at least onemicrostructured surface with a plurality of primary grooves to promotethe unidirectional spreading of the liquids. These primary grooves mayalso contain secondary grooves as in U.S. Pat. No. 5,728,446.

The microstructured flow channels of non-retroreflective microstructuredsubstrates are, in some embodiments, substantially parallel and linearover at least a portion of their length. The channels can be easilyformed from thermoplastic materials by casting, profile extrusion orembossing, preferably by casting or embossing.

The non-retroreflective microstructured substrates are preferably formedfrom any thermoplastic materials suitable for casting, profileextrusion, or embossing including, for example, polyolefins, polyesters,polyamides, poly(vinyl chloride), polymethyl methacrylate,polycarbonate, nylon, etc. Polyolefins are often used, particularlypolyethylene or polypropylene, blends and/or copolymers thereof, andcopolymers of propylene and/or ethylene with minor proportions of othermonomers, such as ethylene/vinyl acetate. Polyolefins have excellentphysical properties, are relatively easy to process, and typically arelower in cost than other thermoplastic materials having similarcharacteristics. Moreover, polyolefins readily replicate the surface ofa casting or embossing roll and are also readily profile extruded. Theyare tough, durable and hold their shape well, thus making such filmseasy to handle after the casting or embossing process. Alternatively,the microstructured substrate can be cast from curable resin materialssuch as acrylates or epoxies, and cured by exposure to heat, ultraviolet(UV), or E-beam radiation. Most likely, the microstructured substrateshaving retroreflective and/or other optical properties discussed ingreater detail below can also be made by the procedures described above.

Another class of microstructured substrates useful in embodiments ofthis invention are retroreflective substrates. Retroreflective materialshave the property of redirecting light incident on the material backtoward its originating source. In situations where the retroreflectivesheeting may need to flex or conform to a surface, a sheeting may beselected, to permit flexing without sacrificing retroreflectiveperformance.

There are two common types of retroreflective sheeting:microsphere-based sheeting and cube-corner sheeting. Microsphere-basedsheeting, sometimes referred to as “beaded” sheeting, is known andemploys a multitude of microspheres, typically at least partiallyembedded in a binder layer and having associated specular or diffusereflecting materials (e.g., pigment particles, metal flakes or vaporcoats, etc.) to retroreflect incident light. Illustrative examples ofsuch retroreflectors are disclosed in U.S. Pat. No. 3,190,178(McKenzie), U.S. Pat. No. 4,025,159 (McGrath), and U.S. Pat. No.5,066,098 (Kult). Microsphere based sheeting does not have a regularpredetermined channel pattern.

Basic cube-corner retroreflective sheeting is known and may be used as adifferentiating component 420 in the articles of the invention. Suchsheeting is frequently used on road signs, safety garments and the like.The sheeting comprises a substantially planar base surface and astructured surface comprising a plurality of cube-corner elementsopposite the base surface. Each cube-corner element comprises threemutually substantially perpendicular optical faces that intersect at asingle reference point, or apex. Light incident on the planar basesurface of the sheeting is refracted at the base surface of thesheeting, transmitted through the sheeting, reflected from each of theof the three perpendicular cube-corner optical faces, and redirectedtoward the light source. The symmetry axis, also called the opticalaxis, extends through the cube-corner apex and forms an equal angle withthe three optical surfaces of the cube-corner element. Cube-cornerelements typically exhibit the highest optical efficiency in response tolight incident on the base of the element roughly along the opticalaxis. The amount of light retroreflected by a cube cornerretroreflective surface drops as the incidence angle deviatessignificantly from the optical axis.

Manufacturers of retroreflective sheeting are known to designretroreflective sheeting to exhibit its peak performance in response tolight incident on the sheeting at a specific angle of incidence. Theterm “entrance angle” is used to denote the angle of incidence, measuredfrom an axis normal to the base surface of the sheeting, of lightincident on the sheeting. See, e.g. ASTM Designation: E 808-93b,Standard Practice for Describing Retroreflection. Retroreflectivesheeting for signing applications is typically designed to exhibit itsoptimal optical efficiency at relatively low entrance angles (e.g.approximately normal to the base surface of the sheeting). See, e.g.U.S. Pat. No. 4,588,258 to Hoopman.

Other applications such as, for example, pavement marking or barriermarking applications, require retroreflective sheeting designed toexhibit its maximum optical efficiency at relatively high entranceangles. For example, U.S. Pat. No. 4,349,598 to White ('598 patent),discloses a retroreflective sheeting design wherein the cube-cornerelements comprise two mutually perpendicular rectangular faces disposedat 45 degrees to the cube-corner sheeting base and two paralleltriangular faces perpendicular to the rectangular faces to form twooptically opposing cube-corner elements. U.S. Pat. No. 4,895,428 toNelson et al. ('428 patent) and U.S. Pat. No. 4,938,563 to Nelson et al.('563 patent) disclose a retroreflective sheeting wherein thecube-corner elements comprise two nearly perpendicular tetragonal facesand a triangular face nearly perpendicular to the tetragonal faces toform a cube-corner. The cube-corner elements further include a nonperpendicular triangular face, all of the aforementioned cube-cornersheeting would be expected to be useful in the articles of the presentinvention. The manufacture of retroreflective cube-corner element arraysis typically accomplished using molds made by different techniques,including those techniques known as pin bundling and direct machining.Molds manufactured using pin bundling are made by assembling togetherindividual pins that each have an end portion shaped with features of acube-corner retroreflective element. U.S. Pat. No. 3,632,695 (Howell)and U.S. Pat. No. 3,926,402 (Heenan et al.) disclose illustrativeexamples of pin bundling. The direct machining technique, also knowngenerally as ruling, comprises cutting away portions of a substrate tocreate a pattern of grooves that intersect to form structures includingcube-corner elements. The grooved substrate is typically used as amaster mold from which a series of impressions, i.e., replicas, may beformed. In some instances, the master itself may be useful as aretroreflective article. More commonly, however retroreflective sheetingor retroreflective articles are formed in a polymeric substrate usingthe master mold or using replicas of the master mold.

Direct machining techniques are a useful method for manufacturing mastermolds for small microcube arrays. Small microcube arrays areparticularly beneficial for producing thin retroreflective sheetinghaving good flexibility. Microcube arrays are also more conducive tocontinuous manufacturing processes. The process of manufacturing largearrays of cube-corners is also relatively easy using direct machiningmethods rather than pin bundling or other techniques. An illustrativeexample of direct machining is disclosed in U.S. Pat. No. 4,588,258(Hoopman).

Master molds suitable for use in forming cube-corner sheeting inaccordance with the '598 patent, the '428 patent, and the '563 patentmay be formed using direct machining techniques as described above.However, the cube-corner geometries disclosed in these patents requiretwo different machining tools to produce a master mold. This reduces theefficiency of the master mold manufacturing process. Additionally,master molds manufactured according to these patents comprise surfacesthat extend substantially perpendicular to the base surface of themaster mold. Such perpendicular surfaces can be detrimental to theprocess of producing exact replicas of the master mold.

It is believed that all cube-corner sheeting discussed in theaforementioned patents would be useful in the articles of the presentinvention. Other microstructured retroreflective substrates which haveprojections other than cube-corners would also be useful in the articlesof the invention. The substrates useful according to the invention mayoptionally have one or more of the following optical characteristics:retroreflectivity, total internal reflection, and partial internalreflection. These include refractive and/or diffractive properties, forexample. The microstructured substrate itself can have specular ordiffusive properties to improve the visibility of the fluid on themicrostructured substrate. As the fluid wets the microstructuredsurface, the difference between the refractive index of themicrostructured surface and the fluid decreases, resulting infrustration of the optical characteristics of the microstructuredsubstrate and improving its transparency.

As previously mentioned, the indicator 414 of the shock indicator 410may comprise a suspension of exfoliated organophilic clay or other solidfiller material with a fluid. Regarding the solid filler material usefulin the formulation of the indicator 414, suitable solids can be selectedand obtained from commercial resources providing the exfoliated claysuch as Nanocor of Arlington Heights, Ill. or Southern Clay Products,Inc. of Gonzalez, Tex. Other useful solid filler materials may comprisesilica particles including hydrophobic silica particles, fumed silicaparticles; bubble and microbubble glass particles; hollow and solidglass spheres; inorganic pigments including titanates and zirconates.Also included would be solid filler materials whose surfaces arechemically and/or physically modified to improve their compatibilitywith the fluid phase of the suspension.

Regarding the fluids available for use in the formulation of theindicator 414, suitable fluids can comprise a variety of materials.These material typically have certain properties that may be beneficialin their use as an indicator material. For example, the surface tensionof the fluid can vary such that the surface tension of the fluid at 23°C. may range from about 10×10⁻³ N/m to about 80×10⁻³ N/m, typically fromabout 10×10⁻³ N/m to about 60×10⁻³ N/m, and often from about 10×10⁻³ N/mto about 50×10⁻³ N/m. Most commonly, the surface tension of the fluidmay range from about 10×10⁻³ N/m to about 40×10⁻³ N/m. The density ofthe fluid can vary. Typically the density of the fluid at 23° C. rangesfrom about 0.5 to about 2 grams/cm³, commonly from about 0.5 to about1.5 grams/cm³, and often from about 0.8 to about 1.5 grams/cm³.Likewise, the zero rate shear viscosity of the fluid can vary at 23° C.from about 1×10⁻³ to about 1×10⁶ Pa-s, typically from about 0.1 to about1×10⁵ Pa-s, and often from about 1 to about 10,000 Pa-s.

The fluid selected for use in the indicator 414 is typically aninnocuous and relatively non-reactive liquid to minimize or eveneliminate undesired reactions or other potentially damaging and/ornon-useful interactions with the other components of the article.Examples of useful relatively innocuous and non reactive fluids include,but are not limited to, the following: silicone fluids such aspolydimethylsiloxane fluids, saturated hydrocarbon-based oils, siliconeoils and gums, mineral oils, glycerols, water, and aqueous based fluids.

The fluid may or may not be colored. In an embodiment, such as thatshown in FIG. 9, where the differentiating component 420 isretroreflective, or where the substrate may have the opticalcharacteristics as discussed herein, the fluid is typically clear andcolorless. As the fluid fills the channels, it causes the total internalreflection to become frustrated. In other words, the substrate thatappeared opaque now appears clear in those areas where the channels arefilled, allowing a viewer (represented by “A”) to observe the coloredcover layer below. The fluid typically has an index of refraction withinabout 0.4 of the index of refraction of the microstructured substratesurface and more typically substantially the same index of refraction.However, the exact nature of the fluid can vary as long as, when it isused in an application where it is intended to render the substratetransparent, it does so sufficiently so one can identify the fluid flowfront by, for example, viewing any color and/or graphics beneath thesubstrate.

When the substrate is not retroreflective or when the substrate isretroreflective but one does not intend to use it in a manner thatcauses it to become transparent, the fluid typically contains pigment(s)and/or dye(s) (such as blue organic dye, for example) and the substrateis selected to provide a contrast to the fluid flow (such as a whiteopaque substrate, for example).

The selection of the fluid and the differentiating component and thepositioning thereof in the shock indicator articles of the invention isaccomplished to allow an observer to view the progress of the fluid overtime as it migrates through the aforementioned channels 421. Dependingon the particular embodiment of the article of the invention an observermay find that the fluid is more readily visible by changing the viewingangle. An observer can readily manipulate the article or change his/herviewing position to find a preferred viewing angle.

Suitable fluids according to the present invention include, for example,viscoelastic and viscous fluids and combinations thereof that providethe desired properties for migration into the channels of themicrostructured surface in response to a shock event of a givenmagnitude. For capillary action to primarily drive the migration of thefluid into the channels of the microstructured substrate, the surfaceenergies of the article components should preferably cause the localcontact angle of the fluid on the microstructured surface of thesubstrate to be less than about 90 degrees, more preferably less thanabout 25 degrees, within the range of intended use temperatures. Thecontact angle is a function of the surface energy of the microstructuredsurface, the surface energy of the fluid (e.g. liquid), and theinterfacial energy between the two.

A viscous material can be defined by analogy to classic viscous fluids.If an external stress is applied to a viscous fluid, it will deform andcontinue to deform as long as the stress is present. Removal of thestress will not result in a return of the fluid to its undeformed state.Such a response is called viscous flow and defines a viscous material orfluid. When there is a direct proportionality between the stress and therate of deformation in a viscous fluid, the fluid is a Newtonian fluid.There are also viscous fluids that are non-Newtonian and which exhibit anon-linear dependence between the stress and the rate of deformation. Inthe articles of the invention, stress results from a shock event of agiven magnitude.

Materials that exhibit both elastic and viscous propertiessimultaneously are called viscoelastic materials. Elastic properties canbe explained with reference to classic elastic solids. Elastic solidsrespond to external stress by deforming and, upon removal of the stress,respond by returning to their original shape. Such a response is calledelastic. Some elastic materials exhibit a direct proportionality betweenthe stress and the deformation, thereby conforming to what is known asHooke's Law. There are also elastic materials that do not obey Hooke'sLaw and that exhibit a non-linear relationship between stress anddeformation. Viscoelastic materials are sometimes classified as eitherviscoelastic solids, i.e., elastic solids that exhibit some viscouseffects during deformation, or viscoelastic liquids, i.e., viscousliquids that exhibit some elastic effects. A viscoelastic liquid can beidentified as a viscoelastic material that continues to deformindefinitely when subjected to a stress.

A viscoelastic material may exhibit a transition from an immobile,glassy state to a viscoelastic liquid state at a temperature known asthe glass transition temperature, T_(g). It may also exhibit atransition from a partially crystalline state to an amorphous state atthe temperature at which the crystalline material melts, T_(m). Often,such a material will behave as a viscoelastic solid below T_(m). Theproperties and the analysis of viscoelastic materials are discussed inJohn D. Ferry, Viscoelastic Properties of Polymers, (John Wiley & Sons,Inc. 1980). Fluids selected for use in the articles of the inventionnormally have T_(g) and T_(m) below the temperatures at which thearticle of the invention is intended for use.

In an article of the present invention, when a viscoelastic material hasbeen selected for use, it is preferred to use a viscoelastic liquidexhibiting small elastic effects, such that it behaves essentially as aviscous fluid in a liquid state at all anticipated temperatures to whichthe article of the invention will be exposed. An illustrative,non-limiting, list of viscoelastic and viscous materials that may besuitable for use as an indicator material in the articles of the presentinvention includes natural rubber; butyl rubber; polybutadiene and itscopolymers with acrylonitrile and styrene; poly(alpha-olefins) such aspolyhexene, polyoctene, and copolymers of these and others;polyacrylates; polychloroprene; polydimethylsiloxane; silicone oils andgums; mineral oils; and block copolymers such as styrene-isoprene blockcopolymers; and mixtures of any of the above.

The viscoelastic materials may, for example, comprise elastomersconventionally formulated as pressure sensitive adhesives. Examplesthereof include, but are not limited to, polyisoprene, atacticpolypropylene, polybutadiene, polyisobutylene, silicone, ethylene vinylacetate, and acrylate based elastomers and can typically include atackifying agent and/or a plasticizing agent.

Monomers useful in making fluids useful in the articles of the inventioninclude, but are not limited to, those that have a homopolymer glasstransition temperature less than about 0° C. Useful alkyl acrylatesinclude, but are not limited to, unsaturated monofunctional(meth)acrylic acid esters of non-tertiary alkyl alcohols having from 2to 20 carbon atoms in the alkyl moiety, typically from 4 to 18 carbonatoms, and often from 4 to 12 carbon atoms. Examples of useful alkylacrylate monomers include, but are not limited to, n-butyl acrylate,hexyl acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexylacrylate, isononyl acrylate, decyl acrylate, dodecyl acrylate, laurylacrylate, octadecyl acrylate, and mixtures thereof.

An example of an optional reinforcing co-monomer is a monoethylenicallyunsaturated monomer having a homopolymer glass transition temperaturegreater than about 25° C. and is preferably co-polymerized with theacrylate monomers. Examples of useful co-polymerizable monomers include,but are not limited to, meth(acrylic) acid, N-vinyl pyrrolidone, N-vinylcaprolactam, substituted (meth)acrylamides such as N,N-dimethylacrylamides, acrylonitrile, isobornyl acrylate, and mixtures thereof.When a copolymerizable monomer is used, the alkyl acrylate is typicallypresent in the composition in amounts from about 50 to 99 parts byweight and the co-polymerizable monomer is typically present incorresponding amounts from 50 parts to 1 part by weight, wherein thetotal amount by weight is 100.

The elastomer can optionally include a tackifier and/or plasticizer in atackifier to elastomer base weight ratio or a plasticizer to elastomerbase weight ratio of typically up to about 2:1. Suitable tackifiersinclude, but are not limited to, hydrogenated rosin esters commerciallyavailable under the trade designations “Foral 85”, “Foral 105”, or“Abitol E” and hydrocarbon tackifiers such as those known as “Regalrez”,all available from Eastman Chemical Company of Kingsport, Tenn. Suitableplasticizers include, but are not limited to, hydrocarbon oils such asthose available under the trade designation “Shellflex” (available fromShell Chemical Co., Houston, Tex., USP grade mineral oil, and phthalatesincluding alkyl phthalates such as dioctyl phthalate, diisononylphthalate, and allyl phthalates.

The article of the invention is preferably designed to providesufficient fluid to fill the channels of the microstructured surface asthe fluid migrates along the channels. The components of the article arenormally chosen to provide a desired rate of migration of the fluid intothe channel structure of the microstructured substrate. In a shockindicator, the fluid such as a viscous liquid, for example, will migratethrough the aforementioned channel structure at a rate that is roughlyproportional to the magnitude of the shock event. By controlling theproperties of the liquid, the indicating device can be constructed toprovide a visually observable indication that the article hasexperienced a shock event exceeding a given magnitude. Accordingly, itis desirable to be able to select a liquid having suitablecharacteristics for the contemplated magnitude of the shock event.Preferably, the viscous fluid also exhibits a yield stress such that thestress created by the shock event exceeds this yield stress allowing thefluid to flow into the channel structure. Such a viscous fluid wouldalso stop flowing when this stress is removed (i.e. when the shock eventis over). The viscous fluid with a yield stress effectively provides andon/off behavior that is desirable in this embodiment. One way ofgenerating a viscous fluid exhibiting a yield stress is to use the solidfiller materials described above along with the appropriate viscousliquid to create a suspension—i.e., a viscous fluid exhibiting a yieldstress or a suspension of exfoliated organophilic clay or other solidfiller material with a fluid such as mineral oil. Other suitable solidfiller materials may comprise silica particles including hydrophobicsilica particles, fumed silica particles; bubble and microbubble glassparticles; hollow and solid glass spheres; inorganic pigments includingtitanates and zirconates. Also included would be solid filler materialswhose surfaces are chemically and/or physically modified to improvetheir compatibility with the fluid phase of the suspension.

The textured or microstructured surface 420 a may be adhered to the basemember 412 using a suitable adhesive which may also comprise a pigmentor other coloring agent. In one such application, a pressure sensitiveadhesive filled with carbon black may be applied to the textured surface420 a to partially cover the texture-imparting structure thereof.Lamination of the textured surface 420 a to the base member 412 createsa series of interconnected microchannels 421 between the laminatedlayers and surrounding but not initially in contact with the indicator414. The channels 421 are initially filled with air when the device 410is in a first configuration (e.g., see FIG. 8), and the properties ofthe differentiating component 420 are such that the resulting laminatedstructure will not reveal the adhesive color under the material 420. Asan alternative to using a colored adhesive layer, the base member 412can be supplied as a colored material. In such a construction theadhesive or other laminating material should be transparent.

When the device 410 is in a second configuration (e.g., FIG. 9)following the occurrence of a shock event, liquid from the indicator 414is released into the annular space 430 of the differentiating component420 where the liquid is then drawn into the microchannels 421 that areprovided between the base member 412 and the surface 420 a. The liquidis pulled into the microchannels 421 by capillary action, and thepresence of the liquid within the microchannels 421 causes a change inthe optical properties of the material 420 to thereby provide a colorchange that can be readily seen by an observer. Such a color change maybe taken an indication that a shock event has occurred.

It will be appreciated that the containment member 418 and the opticalindicator material 420 can be integrated by manufacturing a single filmserving both functions. Those skilled in the art will appreciate that asuitable manufacturing process to produce an integrated top film couldcomprise thermo- or vacuum forming with embossing to produce theprotective dome structure and the diamond grade microstructure in asingle pass for a continuous process. Such a construction iscontemplated within the scope of the invention.

Still another embodiment of a shock indicator device 510 according tothe invention is illustrated in FIG. 10. In the depicted device 510, atransmission layer 530 is provided to reduce, maintain or increase theforce transmitted from or by the shock event. The transmission layer 530is provided and positioned on the base layer 512. The transmission layer530 can be designed to have a damping and/or isolation effect by usingmaterials that provide adherence of the indicator 514 as well asadditionally providing damping and/or isolation properties. In thedepicted embodiment, the base member 512, containment member 518,release liner 526, and adhesive 516 are as previously described. Thelayer 530 may be included in a shock indicator device of the inventionto alter the threshold vibrational frequency and/or the magnitude offorce at which the device 510 will transition from a first condition toa second condition to indicate that a shock event has occurred. Suitablematerials for the transmission layer 530 include those that will providea desired degree of damping and/or isolation. The selection of materialsfor the transmission layer and/or the attachment means will also changethe natural frequency of the indicator 514. The selection of materialsfor the transmission layer and/or the attachment means will combine toeffect the level of force that the indicator experiences. In such aconstruction, the transmission layer 530 will change the level of shockforce that the indicator 514 experiences upon the occurrence of a shockevent.

The shock indicator 514 can be made from materials with high or lowdamping potential, which will affect the amplification factor. Exemplarymaterials for the transmission layer 530 include those described in U.S.Pat. No. 6,456,455, the disclosure of which is incorporated in itsentirety herein by reference thereto. In general the vibration dampingmaterial of the transmission layer 530 will comprise a viscoelasticmaterial or combination of different viscoelastic materials. Suitableviscoelastic materials include those having a storage modulus of atleast about 1.0 psi (6.9×10³ Pascals) and a loss factor of at leastabout 0.01 at the temperature and frequency of use (typically about −60to 100° C.). Those skilled in the art will appreciate that aviscoelastic material is viscous and capable of dissipating energy, yetexhibits certain elastic properties that make it capable of storingenergy in a manner similar to a spring and thus can also have isolationor amplification characteristics based on the material's Tg, geometry,application, and the like.

Those skilled in the art will also appreciate that the transmissionlayer 540 may comprise materials selected to have a certain viscoelasticratio, depending on the ultimate use of the finished shock indicator.For example, a high Tg epoxy at room temperature will have a highmodulus or elastic portion and a very low viscous portion (loss factorless than about 0.15). Or the layer could be a material with a higherloss factor at room temperature with a lower modulus. Viscoelasticmaterials for use in the vibration damping materials normally will havea loss factor, i.e., the ratio of energy loss to energy stored, of atleast about 0.01, often at least 0.15. The loss factor is a measure ofthe material's ability to dissipate energy and depends on the frequencyand temperature experienced by the damping material. More typically, theloss factor for the vibration damping materials is at least about 0.3,normally at least about 0.5, and may reach about 0.7-10 in the frequencyand temperature range where damping is required (generally in the rangeof about 1-10,000 Hz and from −60 to about 100° C., typically in therange of about 50-5,000 Hz and about 0-100° C., and more often in therange of about 50-1500 Hz and about 20-80° C.). As an example of aspecific type of material, a crosslinked acrylic polymer at a frequencyof 100 Hz, the loss factor at 68° F. (20° C.) is typically about 1.0,while at 158° F. (70° C.), the loss factor is about 0.7.

It should be appreciated that the present invention utilizes principlesknown in the art including, without limitation, the relationship betweenforce, mass and acceleration—i.e., Force=(mass)(acceleration).Properties such as, for example, the mass of the indicator or thesubparts thereof, the frequency of the shock event, acceleration,damping, the loss factor, the storage modulus, the loss modulus,isolation, the spring constant, stiffness, the natural frequency, theresonant frequency, the geometry, the configuration of the indicator,and the point of placement on a surface for an end use of the shockindicator can all effect or can influence the design of the shockindicator of the invention. Additionally, environmental conditions(e.g., temperature and humidity) can influence the selection ofmaterials that impact the performance of the shock indicator across therange of end-use environments. In selecting an approach to the design ofa particular shock indicator device, it may be appropriate to considerthese various concepts and/or properties and how they may impact theperformance of the device.

Useful viscoelastic damping materials can be isotropic as well asanisotropic, particularly with respect to elastic properties. As usedherein, an “anisotropic material” or “nonisotropic material” is one inwhich the properties are dependent upon the direction of measurement.Specific viscoelastic materials useful herein include urethane rubbers,silicone rubbers, nitrile rubbers, butyl rubbers, acrylic rubbers,natural rubbers, fluorine-based elastomers and rubbers,styrene-butadiene rubbers, synthetic rubbers, and the like. Other usefuldamping materials include acrylates, epoxy-acrylates, silicones,acrylate-silicone mixtures, cyanate esters, polyesters, polyurethanes,polyamides, ethylene-vinyl acetate copolymers, polyvinyl butyral,polyvinyl butyral-polyvinyl acetate copolymers, epoxy-acrylateinterpenetrating networks and the like. Specific examples of usefulmaterials are also described in or referenced in U.S. Pat. Nos.5,183,863; 5,262,232; and 5,308,887. Examples of thermoplastic materialssuitable for use as the vibration damping material include, but are notlimited to, those selected from the group consisting of polyacrylates,polycarbonates, polyetherimides, polyesters, polysulfones, polystyrenes,acrylonitrile-butadiene-styrene block copolymers, polypropylenes, acetalpolymers, polyamides, polyvinyl chlorides, polyethylenes, polyurethanes,and combinations thereof. Useful viscoelastic materials can also becrosslinkable to enhance their strength and/or temperature resistance.Such viscoelastics are classified as thermosetting resins. During themanufacturing process, the thermosetting resin is cured and/orcrosslinked typically to a solid state, although it could be a gel uponcuring, as long as the cured material possesses the viscoelasticproperties described above. Depending upon the particular thermosettingresin employed, the thermosetting resin can include a curing agent,e.g., catalyst, which, when exposed to an appropriate energy source(such as thermal energy), the curing agent initiates polymerization ofthe thermosetting resin.

It will be appreciated that the properties of the transmission layer canbe changed by the curing process used for the particular polymer systememployed. This could enable a shock indicator to have one set ofperformance criteria during manufacturing and shipping and an alternateset of performance criteria when attached to an end use application. Thesystem could be designed to have high damping and isolation duringmanufacturing and shipping to safe-guard the shock indicator frompremature activation and once applied to the end use application, thepolymer system may be further, or more fully, cured so that the dampingand isolation properties are changed and the indicator will thereafteractivate upon the occurrence of shock event of a predetermined thresholdlevel. Examples of polymer systems for use as transmission layersaccording to the foregoing criteria include pressure sensitive adhesivelayers with at least one epoxy mixture or resin in the layer. In thiscombination, the PSA provides damping and isolation during assembly andshipment. Once the shock indicator is applied to an end use application,the epoxy system in the transmission layer can be exposed to a curingmethod for the epoxy and the Tg is changed to thereby change the dampingand isolation performance of the shock indicator.

It will be further appreciated that the transmission layer and theexternal attachment means can both be selected and designed to providethe same, similar or different damping and isolation characteristics.The shock indicator enclosure construction plus it's attachment meansand the agglomeration construction and its attachment means inside theenclosure can affect the amplification of the vibration or shock forceto the agglomeration in the shock indicator. Likewise, the shockindicator of the invention may be constructed to take advantage of manyor only a few different material properties inherent in the materialsselected for each of the individual components to thereby change theamplification factor that the indicator experiences and the thresholdvalue for the shock event that will cause the shock indicator totransition from a first condition to a second condition. Additionally,the geometry of the components, environmental conditions (temperature,etc.) and the like can all contribute to the threshold at which a shockevent will trigger the shock indicator to indicate the occurrence of theshock event, as described herein. Thus, it will be understood that thematerials and components used in the construction of the shock indicatordevice of the present invention can all be used to change theisolation-damping-amplification-transmissibility properties of the shockindicator device, thus changing how the indicator responds to aparticular shock event.

The vibration damping material used in the transmission layer canoptionally include additives such as fillers (e.g., talc, etc.),colorants, toughening agents, fire retardants, antioxidants, antistaticagents, and the like. The vibration damping material can optionallycontain fibers and/or particulates additives that are designed toprovide an increased thermal and/or electrical conductive path throughthe vibration damping material.

It will be appreciated that the manufacture of the foregoing embodimentcan be accomplished according to the above described manufacturingmethod by incorporating another line for the lamination or attachment ofthe transmission layer to the base layer or to the differentiatingcomponent described herein. As mentioned, the materials used for thetransmission layer may be provided as a pressure sensitive adhesive orother form of adhesive material that provides the means for attachingthe transmission layer to the base or the differentiating layer. Othermaterials may require additional means for affixing these components toone another such as the application of additional adhesive layer(s),calendaring with heat and pressure, and the like. Such methods are wellwithin the skill of those practicing in the field and are not furtherdescribed herein.

Regarding applications, the shock indicator of the present invention maybe applied to any of a variety of devices where it may be appropriate ordesired to monitor in a passive mode any and all shock eventsexperienced by the device. In particular, cellular telephones and otherhand-held electronic devices are particularly suited to be equipped withthe shock indicator of the invention. One particular applicationinvolves the placement of the indicator of the invention in a cellulartelephone. Current warranty practices within the cellular industrypreclude warranty coverage where the user has abused the device. Hence,the shock indicator of the invention may be used in conjunction withcellular telephones as a means to determine whether the telephones haveexperienced a shock event caused, for example, by dropping the telephonefrom a significant height onto a hard surface such as concrete or thelike. Similar applications also exist for other hand-held devices aswell as any variety of electronic components and equipment. In view ofthe foregoing applications, it will be appreciated that the size of theshock indicator may be an important feature. Use of the shock indicatorinside of a hand-held device will typically require that the indicatorbe relatively small.

When placed in association with a device, consideration should also begiven to the hardness of the surface to which the shock indicator isbeing affixed because the placement of the shock indicator in an end useapplication will also affect the shock indicator's apparent performance.If the shock indicator is placed onto a very rigid portion of a rigidstructure, the shock indicator will perform differently than if theindicator is attached to another portion of the structure that isisolated from the stiff structure that is encountering the shock orvibration event.

In still another embodiment of the invention, multiple levels ofactivation may be indicated within a single shock indicator. Asmentioned herein, the cohesive character of the agglomerated indicatorcan be modified by the presence of a small amount of an oil or otherorganic diluent or agglomeration aid. Mineral oil, for example, may beused as an agglomeration aid in agglomerating the powder indicators ofthe invention. Levels of the agglomeration aid in the agglomeratedpowder are typically very low, and as little as about 2 wt. % mineraloil has been used. As the mineral oil concentration in increased, thethreshold level of force also increases (e.g., the minimum amount offorce required to transition the indicator from the first state to thesecond state). The maximum level of mineral oil in the particleagglomeration is limited by the volume ratio of the oil and the solidparticulate at which the particles become a discontinuous phase whilethe liquid becomes a continuous phase. In providing multiple levels ofshock indication in a single indicator, it has been found that varyingthe concentration of the agglomeration aid can change the thresholdlevel at which the indicator transitions from a first configuration to asecond configuration following a vibrational shock so that the shockindicator can be observed in a second or activated state.

In the contemplated embodiment, two, three or more colored indicatorcompositions of an agglomerated powder can be used to indicate differentlevels of vibrational or inertial shock. In this embodiment each of theagglomerated powder indicators is typically formulated to comprise thesame powder materials with each of the indicators having differentlevels of mineral oil therein. In the manufacture of such an embodiment,a dispersion of the powder and mineral oil may be placed in discreteindependent dots around a central area on a base member and thereaftercovered with a containment member such as a protective dome. An organic(e.g., hydrocarbon) diluent may be added to the mixture of powder andoil to allow for the preparation of a slurry with binder and powder. Thediluent is typically selected to be volatile so that it will evaporateafter the slurry is deposited on the base member, thereafter leaving theagglomerated powder indicator. The base member may be treated in amanner that enhances the color or visual differences between the powderand the materials of the base member. For example, polyester film may betreated with a black aluminum oxide evaporation process, such as thatdescribed in U.S. Pat. Nos. 4,430,366 and 5,766,827, to produce a blackfilm that will serve as a base member with sufficient color contrast topermit a quick visual confirmation of the state of each of theagglomerated indicator powders. In such a construction, a deviceassociated with the shock indicator may then be subjected to vibrationalshocks of different magnitudes. The agglomerated indicator comprisingthe lowest amount of mineral oil will be the first to transition to asecond configuration. On subsequent increasing shock treatments theother agglomerated indicators will also disperse at progressivelygreater vibrational shock levels.

In addition to the inclusion of multiple indicators within the sameshock indicator, it is within the scope of the invention to include morethan one shock indicator, such as the shock indicator embodiments shownin the various Figures herein, in association with a single device. Eachof the different shock indicators may be constructed to transition fromthe agglomerated or first state to a dispersed or second state upon theoccurrence of shock events of different magnitudes.

In still another embodiment of the invention, a wetness indicator may becombined with the shock indicator of the invention to provide a combineddevice capable of passively showing exposure of the shock indicator tovibrational or inertial shocks as well as showing whether an associateddevice has been exposed to water or other forms of moisture. A suitablewetness indicator that can be incorporated into the shock indicator ofthe invention include conventional wetness indication paper comprising awhite paper base, an indicator dye and pressure sensitive adhesive.Where the powdered agglomerated indicators do not contain water, theindicator can be applied to a white paper base in the same way as itwould otherwise be applied to the above described polymeric film. Asuitable wetness indicator that may be combined with the shock indicatorof the present invention includes that described in co-pending U.S.patent application Ser. No. 09/972,124, filed Oct. 1, 2001, entitled“Water Contact Indicator,” the disclosure of which is incorporated inits entirety herein by reference thereto.

In still another embodiment, the protective film structure of thecontainment member may comprise dimples, intrusions, protrusions,multiple layers and/or different material layers that change the opticalcharacteristics of the protective film. The inclusion of these featurescan also be, at least in part, for the purpose of changing the strengthof the protective film structure.

In still another embodiment, the indicator can comprise primary andsecondary matrices wherein the first matrix is an agglomeration ofpowder particles and the second matrix is comprises larger glass bubblesor beads (or other similar objects). The larger components of thesecondary matrix provides a structure for the smaller primaryagglomerated powders to further attach and also can provide a structurewith greater X-Y-Z dimensions and stability with a larger primaryagglomeration overall versus a agglomeration with no secondary matrix.This construction can also be designed so that the larger matrix will“break free” from the attachment location within the enclosure while thesmaller powder particles become fractured from the secondary matrix. Ina variation of the foregoing embodiment, the smaller powder particlesbreak free of the larger secondary matrix upon experiencing a firstlevel of shock while the larger matrix can be positioned within theindicator device to break free at its attachment points upon theoccurrence of a second (e.g., higher) level of shock. The secondarymatrix can comprise one or more larger particles of any of a variety ofgeometries and sizes including larger those mentioned herein such asbeads, (e.g., glass, plastic or ceramic) as well as metal beads (e.g.,ball bearings).

In still another embodiment, the containment member of the shockindicator is attached to a desired location with an attachment meanssuch as an adhesive provided in a discontinuous coating or one thatutilizes a smaller or larger area than actual base of the shockindicator. In this construction, attachment can occur with one, two,three or more individual attachment points between the base of the shockindicator and the surface of the desired object.

In still another embodiment, the shock indicator contains the abovedescribed indicator comprising agglomerated particles of powder or thelike. Additionally, one or more objects may can be attached (loose orfirmly) or be free to move about the enclosure, so that the objectsimpact the agglomerated powder during a shock event to aid in thefracture of the powder agglomeration and the indication of a desiredshock event. The impingement objects could be glass beads, bubbles, BB'sand the like, and the masses, sizes and shapes of the objects can bechanged to achieve a desired movement within the containment member ofthe shock indicator. If the containment member is provided with dimplesor other surface structures, these structures can help to direct theobjects in striking the agglomerated powder when a shock event occurs.Moreover, the additional objects can be designed or selected to providea significant force when accelerated within the confines of thecontainment member during a shock event.

In another embodiment of the invention, the indicator can includeprimary and secondary subparts wherein the primary subparts are largerobjects and the secondary subparts are smaller objects such as thepowder particulates described herein. The secondary subparts agglomeratearound one or more primary subparts to form a single mass useful as anindicator. The primary subpart(s) may be attached to the base with thesecondary subparts agglomerated therearound. A shock event causes theprimary subparts to dislodge from the base and the associated movementof the mass breaks apart the associated secondary subparts, providingshock indication. The primary subparts could comprise one or more masseswith an associated agglomeration of the secondary subparts agglomeratedaround the primary subpart(s). Each primary subpart(s) could be the sameor different as other primary subparts.

In another embodiment of the invention, the indicator can be positionedwithin the containment member so that a shock event from any directionwill impart substantially the same shearing, compression, tension,cleavage and/or peel forces into the indicator. A means for positioningthe indicator within the device might be to have more than oneattachment point for positioning the indicator within the device.Attachment points may be provided to facilitate the attachment of theindicator to the base member and/or to the other components of thedevice such as an attachment point to the internal surface of thecontainment member, for example. Such a means for attaching theindicator might be considered a multi-axis attachment.

In another embodiment of the invention, single or multiple masses may beadded to the shock indicator enclosure interior and/or exterior surfacesto further modify the response of the shock indicator to a shock event.The modified response of the shock indicator may be determined by theamount and/or number of additional mass added to the device as well asthe position of the masses within the containment member of the shockindicator device.

In another embodiment of the invention, the indicator comprises aviscous liquid with one or more shear plane surfaces within the liquid.The liquid is as described elsewhere herein along with one or moremasses or added shear plane geometries (glass beads, bubbles, BB's,pins, posts, etc.) that can be of various sizes and shapes that aid inthe shear thinning of the liquid in response to a shock event. Themasses increase the shear force into the fluid and provides additionalshear thinning planes or surfaces.

In still another embodiment of the invention, the indicator can comprisea combination of colored materials that will facilitate the visualdetermination of whether the indicator has transitioned form the firststate to the second state following a shock event. For example, theindicator may comprise a first agglomerated powder present at a lowconcentration in a first color and the second agglomerated powderpresent at a high concentration in a second color. In a first stateprior to a shock event, the colors of the two agglomerated powdersappear distinct and both colors are visually observable to an observer.In a second state following a shock event, the two agglomerated powdersbecome dispersed and, in the dispersed state, will appear as a singlecolor, typically as the second color due to the lower concentration ofthe first powder and the mixing of the powder particles that occurs whenthe particles are dispersed.

While various embodiments of the invention have been described indetail, it should be appreciated that the invention is not limited tothe specific constructions that have been described. Changes to thebasic construction are possible such as by adding additional film layersto the base member that serve one or more additional functions in theoperation of the finished shock indicator device. For example, atamper-indicating shock indicator device may comprise layers of (a) aplanar, light-transmissive layer; (b) a light-transmissive imagedrelease coating; and (c) an adhesive layer; in which (i) the image isnot visible until becoming permanently visible when the release coatingis separated from the other layer(s); and (ii) the assembly cohesivestrength of the indicator device ensures that the device remains as asingle unit after the release coating is separated and the image isseen. Such layers are described in U.S. Pat. No. 5,770,283 to Gosselinet al. Additionally, the exact ordering of the components and the orderof the manufacturing steps in the above described method may be changedwithout changing the basic construction of the invention—i.e., a baseand an indicator that is capable of being presented in one configurationprior to the experience of a shock event and which presents itself in asecond configuration in response to a shock event to indicate to anobserver that the device has experienced such a shock event. Theindicator device of the invention can be constructed to increase or todecrease the sensitivity of the device to customize the device totransition for the first configuration to a second configuration onlywhen the predetermined threshold shock has been experienced by thedevice. In this manner, the invention provides a shock indicator thatcan be customized for a particular application where shock indication isappropriate only for shock events exceeding a threshold value at whichcomponents or the like of the associated electronic or other device aremore likely to experience damage or harm from such a shock event.Additional unforeseen changes and modifications to the describedembodiments may also be possible which also may be equivalents to thecomponents described herein. All such modifications are contemplated asbeing within the scope of the invention, as generally set forth in thefollowing claims.

1. A method for the manufacture of a shock indicator, comprising: (A)providing a base comprising a first surface and a second surface, thesecond surface of the base associated with an attachment means; and (B)placing an indicator in association with the first surface of the base,the indicator comprising an agglomerated powder comprising powderparticles arranged (i) in a first configuration when the shock indicatoris in a first state prior to a shock event, and (ii) in a secondconfiguration when the shock indicator is in a second state following ashock event, wherein placing an indicator in association with the firstsurface of the base comprises depositing a slurry in association withthe first surface and thereafter drying the slurry.
 2. The method ofclaim 1 further comprising placing a containment member over the firstside of the base and over the indicator, the containment member beingtransparent, thereby facilitating the visual determination of whetherthe indicator is in the first configuration or the second configuration.3. The method of claim 1, further comprising providing a means forattaching the indicator to another surface.
 4. The method of claim 1wherein placing an indicator in association with the first surface ofthe base further comprises placing a plurality of indicators inassociation with the first side of the base, each indicator comprising aplurality of powder particles arranged (i) in a first configurationprior to a shock event, and (ii) in a second configuration following ashock event.
 5. The method of claim 1 further comprising associating anelectronic device with the shock indicator, the device selected from thegroup consisting of cellular telephone, personal digital assistant, handheld computer and digital camera.